Answer by Jan Haywood
This is a big question, which probably deserves its own lecture course! I will include here what, I think, are just a few particularly salient points. First of all, Herodotus’ Histories are a key narrative source for a major set of conflicts between the Achaemenid Empire and various Greek poleis (city-states), known as the Greco-Persian Wars (490-479 BCE); these conflicts proved to be a significant series of events, shaping relations between Persia and Greece long afterwards! Of course, Herodotus was far from the only author in antiquity to write about the Greco-Persian Wars. Others who did so include Diodorus, the Sicilian historian of the first century BCE (who seems to have been influenced by Herodotus’ work), as well as Plutarch, the biographer and historian from the first-second centuries CE, who famously criticised Herodotus’ account of the Greco-Persian Wars in his de malignitate Herodoti (On the Malice of Herodotus).
But Herodotus’ work is an incredibly rich one, and its importance extends far beyond what it can tell readers about the military conflict between Greece and Persia. Herodotus displays a keen interest in the customs, geography and culture of various peoples, not least the Egyptians, to whom he devotes an entire book (i.e. Book 2). (The Histories are conventionally divided into 9 books, though Herodotus is not responsible for these divisions.) His work is also rich in information concerning the religious history of the ancient Greek world, and it tells readers a great deal about non-Greek religions too. (Various recent publications have further enriched our understanding of this topic, for example, Andreas Schwab, Fremde Religion in Herodots Historien, Stuttgart 2020).
I don’t have the space to go into much detail here, but many readers have also derived great joy from numerous of Herodotus’ celebrated stories concerning particular individuals. For example, his account in Book 1 on the rise and fall of the Lydian king Croesus, as well as his account in Book 3 on Polycrates, the tyrant of Samos from the 540s – 522 BCE.
Finally, I will add that Herodotus has been hugely influential since antiquity in several ways. Not only does he stand as a key figure in the development of history-writing, but he also stands at the forefront of other fields of study, such as geography, ethnography, travel-writing, etc. The academic study of Herodotus’ impact in later periods and the reception of his work is now a burgeoning field, which continues to improve and refine our understanding of why Herodotus has been so important since classical antiquity. If you are interested in finding out more about this aspect of Herodotean research, a good place to start is Jessica Priestley and Vasiliki Zali’s excellent collection, Brill’s Companion to the Reception of Herodotus in Antiquity and Beyond, Leiden and Boston 2016.